1. Field of the Invention
The present invention relates in general to the field of information handling system distributed capacitance, and more particularly to a system and method for reducing the effect of distributed capacitance associated with light generation to illuminate a liquid crystal display using Cold Cathode Fluorescent Light (CCFL).
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling systems are sometimes assembled in portable configurations to allow a user to operate the information handling system independent of external peripherals and external power. Typical portable information handling systems include an integrated power supply, such as an internal rechargeable battery, and an integrated display, such as a liquid crystal display (LCD) integrated in a lid that opens for operation and shuts for storage. The LCD generates a display by altering the light-passage characteristics of pixels so that light that passes from the back of the display through the pixels presents a desired image. The backlight that generates light to illuminate the pixels is typically a fluorescent light, such as a cold cathode fluorescent lamp (CCFL), aligned along an edge of the display to pass light through a light guide for even distribution across the display. Generally, the CCFL is placed in a semi-circle shaped reflector to direct light into the light guide.
CCFL lights are typically used as portable display backlights due to the relatively effective illumination provided with relatively low power consumption and heat generation. Often, portable information handling system displays are the system component that takes the greatest toll on internal battery charge life when the information handling system operates on internal power. Internal battery direct current power is converted to high voltage and high frequency alternating current with an internal inverter, such as voltages of approximately 600 Volts and frequency of approximately 50 KHz. One difficulty that arises with the transmission of high voltages and frequencies through a CCFL is that the passage of the current through the CCFL gas plasma results in generation of distributed capacitance where grounded metallic surfaces are proximate to the CCFL. For example, the semi-circle shaped reflector that directs light to the light guide is typically metallic and generally grounded for ease of assembly and reduced electromagnetic emissions (EMI). The proximity of the reflector to the lamp and its length form one side of the distributed capacitance that affects power transmitted from the inverter to the ground of the lamp. Distributed capacitance often increases power consumption by 10 to 20% and also impacts the quality of light produced by making the brightness across the lamp uneven. Increased power consumption due to distributed capacitance of the lamp and wiring to system ground thus may have a substantial negative impact on a portable information handling system's battery charge life.